i am highly against using any form of blob fields especially in MySQL. You lose performance, overall scalability (if your image catalog gets big enough), etc, etc.. (google mysql blob disadvantages)
Store paths in your db and use lightspeed to serve static images on another subdomain.
but the answer to your problem is BLOBs are streamed from mysql. You need to output the image buffer directly to the browser.
JSP isn't good at outputting binary streams to clients, use a servlet to return mime/*whatever your image type* content.